For nearly two decades, the National Institute on Drug Abuse and it's predecessor, Center for Studies of Narcotics and Drug Abuse, NIMH, has provided the scientific community working on problems of drug abuse with authentic, standardized supplies of controlled research drugs and chemicals. These include marijuana cigarettes, known hallucinogens, heroin, amphetamines, cannabinoids, and many other drugs essential for both clinical and laboratory -research studies. Recently, the isolation of Leu5-enkephalin, Met5-enkephalin, and other opioid peptides has generated an explosive interest in this research area. This active research area has generated the need for several opioid peptides and respective radiolabeled compounds in large guantities. The peptides are needed for a number of preclinical and clinical studies supported by NIDA--receptor-binding studies, evaluation of addiction and analgetic potential, pharmacokinetic studies, conformational studies by C.D.; N.M.R.; X-ray, laser-Raman, FT-IR, etc. Opioid peptides and their respective radiolabeled compounds are expensive and purity is not always sufficiently established. In order to meet the demand for pure, authentic compounds, NIDA plans to continue to maintain an inventory of about 10-15 peptides and their respective radiolabeled compounds for use in NIDA supported studies. Through this contract NIDA plans to continue to supply chemically pure, racemization-free peptides primarily to NIDA grantees and at the same time maintain capability to rapidly synthesize, on demand, new compounds that are potentially useful.